1. Field of the Invention
The present invention generally relates to a plastic injection moulding apparatus in which in each cycle of moulding operations, a plastic injecting nozzle is advanced and is pushed against the gate of a metal mould into which plastics material is injected to mould it. More particularly, the present invention relates to a device for reshaping a recessed gateway, that is the sprue bush inlet, of a metal mould to its original shape when the gateway recess has become worn and deformed by repeated contact with the injecting nozzle tip of a plastic moulding apparatus.
2. Description of the Prior Art
When the metal mould has become worn and deformed at its gateway recess, an undesired gap or space appears between the tip of the plastic injecting nozzle and the metal mould when these parts are brought into contact with each other. This allows molten plastics material to leak out and become hard around the undesired gap where it forms an irregular projection from the plastics moulding. When such a plastics moulding is removed from the metal mould, the undesired irregular projection may be disadvantageously trapped by the metal mould preventing release of the moulding. When this happens it is necessary to reshape the worn part of the metal mould to the exact original shape. The required reshaping has been hitherto performed with the aid of a machine tool. To do this, the heavy metal mould must be removed from the injection moulding apparatus and be placed in position in the machine tool. After being reshaped the heavy metal mould must be removed from the machine tool and be put back in position in the injection moulding apparatus. This requires much labour and time, and the moulding work must be interruped all this while. Accordingly the moulding efficiency will be lowered. With this problem in mind, the object of the present invention is to provide a mould reshaping device which permits the reshaping of the gate recess of a metal mould to the exact original shape without removing the mould from the injection moulding apparatus.